UV radiation curable epoxy functional silicones are well known as are photocatalysts therefor. These silicones are utilized as adhesive release coatings, as coatings for optical fiber, as conformal coatings for electronic devices and so forth.
U.S. Pat. No. 4,576,999 to Eckberg discloses epoxy and/or acrylic functional polysiloxanes as UV radiation curable adhesive release coatings. The catalyst may be a photo-initiating onium salt and/or a free radical photoinitiating catalyst. U.S. Pat. Nos. 4,279,717 and 4,421,904 to Eckberg, et al., discloses epoxy functional diorganosiloxane fluids combined with iodonium salts to form UV radiation curable adhesive release compositions. U.S. Pat. No. 4,547,431 discloses epoxy functional diorganosiloxane combined with onium salt catalyst and polyfunctional epoxy monomers to also form an adhesive release coating. The polyfunctional epoxy monomer may be organic or silicone and is added to control release.
The combination of epoxy functional silicone and onium salt photocatalyst displays a fast non-inerted UV cure response. However, despite many positive features, the combination has significant shortcomings. Foremost among these shortcomings, the epoxy functional silicone has a limited capacity to solubilize certain dye sensitizers and onium salt photocatalysts, which reduces the effectiveness of these materials. The onium salts are a favored photocatalyst for epoxy materials, thus solubility of these salts in the composition to be cured is of significant interest.
It is an object of the present invention to improve the compatibility of epoxy functional silicone with onium salt catalyst.
It is yet another object of the present invention to improve performance and usefulness of epoxy functional silicones in combination with onium salt photocatalysts by simple modification of epoxy functions.